1. Field of the Invention
The present invention relates to the field of inspection equipment and more particularly to equipment for automatically detecting the presence of certain liquids and foreign objects in containers.
2. Prior Art
Electronic bottle inspectors for inspecting the interior of empty bottles for opaque foreign matter are well known in the prior art. Examples of such prior systems include those disclosed in U.S. Pat. Nos. 3,133,640 and 3,415,370. The latter patent is of particular interest as the present invention comprises a modification of a prior art system very similar to that disclosed in that patent. Such incorporation systems are generally characterized by a means of support of the bottle to be inspected from the side thereof with a light source, frequently an incandescent light source, below the bottle to direct light through the bottom thereof. Light passing through the bottom of the bottle and upward through the neck of the bottle is generally focused thereabove to provide an image of the bottom of the bottle, with some form of scanner or sensor array for sensing different portions of the image to determine relative light and dark areas, the dark areas, of course, representing the presence of opaque objects.
In the system of U.S. Pat. No. 3,415,370 the light passing through the bottom of the bottle and upward through the neck is focused by a lens thereabove onto the face of a rotating scanner, characterized by a concave surface having a non-reflective background with a single mirror segment thereon for sweeping the image focused onto the scanner. The axis of rotation of the scanner is inclined somewhat to the axis of the bottle so that the portion of the image reflected by the reflective portion of the scanner, being focused by the concave curvature thereon, is focused onto a detector displaced somewhat to the side of the focusing lens. The system of that patent also incorporates a neck inspection feature which could be utilized with the present invention, though in the preferred embodiment is not.
Equipment generally in accordance with U.S. Pat. No. 3,415,370, though not incorporating the neck inspection feature, has been manufactured for a number of years by Industrial Automation Corporation of Santa Barbara, California, assignor of the present invention. In that equipment a pair of approximately diametrically opposed mirror segments are utilized on the rotating scanner, and a bottle support mechanism generally in accordance with U.S. Pat. No. 3,975,260 is utilized.
The infra-red radiation absorption characteristics of water and water vapor are well known. (See for example, U.S. Pat. Nos. 2,703,844 and 3,021,427 and 3,089,382 and 3,153,722, and also Wood, the review of Scientific Instruments, Vol. 29, No. 1, pages 36-41, January 1958.) These absorption characteristics have been used to detect the presence or absence of a liquid at a particular level in a container, such as in U.S. Pat. No. 3,225,191, and to measure the relative amounts of water in containers such as in U.S. Pat. No. 2,321,900. The fact that infra-red energy may pass through containers which are relatively opaque to visible light is disclosed in the last stated patent, as well as U.S. Pat. No. 2,945,588. Other patents utilizing the absorption characteristics of water for detecting purposes includes U.S. Pat. No. 3,150,264 and No. 3,043,956, and for the detection of foreign matter in liquids using infra-red energy in U.S. Pat. No. 2,132,447.
Finally a system for inspection of empty beverage bottles is described starting on pages 52 and 53 of Food Processing, March, 1978. In accordance with that disclosure the bottom of a bottle is inspected from above for contaminants utilizing a dual inspection system comprised of superimposed radial and raster scanners. A beam splitter diverts a portion of the light gathered from the bottle bottom by the lens system and directs it to the raster scanner that gives uniform inspection over the center portion of the container. A coaxial radial scanner receives the remainder of the light and processes a portion of it to scan the outer portion of the container. The coaxial radial scanner system allows part of the light to pass on to the residual liquid detector that uses an infra-red scanner to detect the presence of minute amounts of water in the bottle. It is unknown at this time whether this system constitutes prior art, i.e. has priority of invention over the present invention.